1. Field of the Invention
The present invention relates to a lumbar support device provided in a powered seat of an automobile, and is particularly directed to a method for controlling the lumbar support device under a motor control so as to adjust the fore-and-aft position of the same for a proper support of the lumbar portion of an occupant on the seat and a motor control device provided in the seat in association with such method.
2. Description of Prior Art
In automotive seats, it is well known that a lumbar support device is provided in some of them as a means for giving a proper support to a lumbar part of an occupant sitting on the seat, with a view to making stable his or her seating posture and protecting him or her against a fatigue developed from a long period of seating in the seat. The lumbar support device is designed to cause movement of a lumbar support plate which gives a pressure support to the occupant's lumbar part. The control of such lumbar support plate (for the for-and-aft movement of the same) is typically made through control of associated motor by manual switch operations.
In connection with the lumbar support, it has been found from the recent experiments and resarches that the spine or vertebra of a person who sits on a seat with the smallest fatigue represents an inverted "S" shape, which has led us to presume that a deformation of such inverted-S-shaped vertebra appears to create a fatigue or a tired feeling in the person on the seat. It is therefore thought that the fatique or tired sense originates from a muscular fatigue which arises from an uneven force distribution of the person's muscle due to the foregoing deformation of inverted "S" shape of vertebra.
With this diagnostic aspect in view, most of known lumbar support devices are so designed that its lumbar support plate may be adjusted in support force against the person's lumbar part such as to keep his or her vertebra in that ideal inverted "S" shape in order to eliminate the fatigue.
However, the hitherto lumbar support plate does not take into account the fact that a long period of sitting on a seat leads soon to the muscular fatigue of passenger thereon and consequently the passenger changes his or her seating posture, encountering again the deformation of vertebra from the inverted "S" shape and thus suffering from the foregoing fatigue problem. The reason is that, according to this known device, the lumbar support plate, which contacts the back of passenger, is normally kept stationary and applies a predetermined support force, constantaly, to that back portion or lumbar part of passenger at a given pressure amount for attaining the ideal inverted "S" shape of vertebra. In other words, the device merely gives such support force to the passenger's back, and the passenger is forced to be restrained under such fixed conditions, which results in causing easy creation of the muscular fatigue on the contrary and does not attain the vertebra's inverted "S" shape properly depending upon the seating state of the passenger on the seat.